India’s biggest airline, IndiGo, has been forced to ground 13 planes and cancel 84 flights because of issues withthe Pratt and Whitney made engines on its Airbus A320 neo aircraft.

IndiGo and rival GoAir have been facing delays in receiving planes from Airbus due to continuing problems with engines developed by Pratt and Whitney, owned by United Technologies. IndiGo, which flies four in every 10 Indian air passengers, operates hundreds of flights each day.